1. Field of the Invention
The present invention relates in general to data transmission systems, and in particular to data transmission systems which may be utilized in wellbores to communicate coded messages through fluid columns disposed therein.
2. Description of the Prior Art
In the oil and gas industry, it has been one longstanding objective to develop data transmission systems which do not require the utilization of electrical conductors to carry coded signals between wellbore locations which are separated by great distances. Experience has revealed that data transmission systems which require the utilization of electrical conductors extending between communication nodes in a wellbore are advantageous when data must be communicated within the wellbore at extremely fast transmission rates, or when large blocks of data need to be transferred between communication nodes; however, the utilization of electrical conductors has several serious disadvantages including: (1) since most wellbores include regions which are exposed to corrosive fluids and high temperatures, a long service life cannot be expected from a data transmission system which utilizes electrical conductors; (2) since most wellbores extend for substantial distances, data transmission systems which utilize electrical conductors are not generally considered to be cost effective, particularly when such systems are utilized only infrequently, or in a limited manner; (3) since all wellbores define fairly tight operating clearances, utilization of a wireline conductor to transmit data may reduce or diminish the operating clearance through which other wellbore operations are performed; and (4) since wellbores typically utilize a plurality of threaded tubular members to make up tubular strings, utilization of an electrical conductor to transmit data within the wellbore complicates the make-up and break-up of the tubular string during conventional operations.
Accordingly, the oil and gas industry has moved away from the utilization of electrical conductor data transmission systems (frequently referred to as xe2x80x9chardwirexe2x80x9d systems), and toward the utilization of pressure changes in a fluid column to transmit data within the wellbore. One example of the extensive use of fluid columns within a wellbore to transmit data is that of measurement-while-drilling data transmission systems, also referred to as xe2x80x9cMWDxe2x80x9d systems. Typically, these systems are utilized only in drilling operations. Generally, a plurality of sensors are provided in a tubular subassembly located within the bottom hole assembly, near the rock bit which is utilized to disintegrate the formation. The electrical sensors detect particular wellbore parameters, such as temperature, pressure, and vibration, and develop electrical signals corresponding thereto. The electrical signals are converted into a digital signal stream (generally multiplexed sensor data) and utilized to develop a plurality of pressure changes in a fluid column, typically the tubing fluid column, which are sensed at the earth""s surface and converted into a format which allows the drilling engineers to make decisions which affect the drilling operations. Some attempts have been made to apply the concepts of MWD data transmission systems to completion operations, during which the drilled wellbore is placed in condition for continuous production of oil and gas from selected wellbore regions. To date, no entirely satisfactory data transmission system has been developed for utilization in completion operations, nor has a satisfactory data transmission system been developed for utilization during prolonged production periods.
At present, several standard approaches are utilized to operate wellbore tools which are remotely located within a wellbore on a workstring. One approach is to increase the pressure of fluid disposed within the central bore of the workstring until a predetermined pressure threshold is exceeded, causing the shearing of set screws or other similar pressure-sensitive mechanical latches. Another approach is to utilize a slickline to pass an actuating tool, with a particular profile, into contact with a profiled component on the wellbore tool. Yet another approach is to utilize an electrical-conductor (commonly referred to as an xe2x80x9cE-linexe2x80x9d) to energize an electrically-actuated substance which operates mechanical components to switch a wellbore tool between modes of operation.
It is one objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein potential fluid leak paths are minimized in general, and in particular are minimized by sensing the coded messages through a rigid structural component of the reception apparatus at the reception node.
It is another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein changes in circumferential stress applied to a rigid structural component at the reception node are utilized to detect the coded message in the fluid column.
It is yet another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein changes in the elastic deformation of a rigid component at the reception node are utilized to detect the coded message in the fluid column.
It is still another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein the opportunity for error in the transmission and reception of coded messages is minimized by providing a coded message which is composed of a plurality of message segments which comprise the presence or absence of a rapid rate of change of fluid pressure magnitude within the fluid column at particular locations on a time-axis.
It is still another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein the coded message is composed of a plurality of message segments, each of which corresponds to the presence or absence of a rapid rate of change of the pressure amplitude within the fluid column, wherein filters are utilized to eliminate the influence of pressure changes which fall below or above predetermined rate thresholds.
It is yet another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein the apparatus includes an electromagnetic reception system for receiving electromagnetic signals which are utilized to train a microprocessor to switch one or more electrically-actuated wellbore tools between selected operating modes in response to detection of a coded message in said fluid column.
It is still another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, with a reception apparatus located within the wellbore at a desired location on a wellbore tubular conduit string, wherein the reception apparatus is partially composed of a substantially imperforate mandrel member through which the coded messages are detected.
It is yet another objective of the present invention to provide a method and apparatus for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, wherein the operative components of a reception apparatus are maintained out of direct contact with said fluid column, and wherein said reception apparatus is utilized to detect, through a substantially imperforate conduit member, the coded message which is impressed upon said fluid column.
It is still another objective of the present invention to provide a pressure pulse generation apparatus which is utilized to provide rapid changes in pressure which are detectable at remote locations within the wellbore, but which does not utilize a large volume of fluid, and which does not substantially change the absolute volume of the fluid within a particular wellbore fluid column which comprises a communication channel.
It is yet another objective of the present invention to provide a method and apparatus for communicating coded messages within a wellbore, wherein the coded messages are defined by operator-selectable coded messages attributes of: (a) the number of consecutive rapid pressure changes within a fluid column; and (b) the time interval between consecutive rapid pressure changes, which distinguish one particular coded message from other coded messages.
It is yet another objective of the present invention to provide an apparatus for communicating coded messages within a wellbore between a transmission node and a reception node, through a fluid column extending therebetween, which includes (1) a transmission apparatus at the transmission node which is in communication with the fluid column for generating at least a portion of the coded message, and (2) a reception apparatus at the reception node for detecting changes in at least one fluid column attribute, with the reception apparatus including a plurality of power-consuming electrical components, wherein, during a communication code mode of operation at least a portion of the power-consuming electrical components are maintained in an off condition until at least one change in said at least one fluid column attribute is detected by the reception apparatus.
It is yet another objective of the present invention to provide an apparatus for communicating coded messages in a wellbore which includes a transmission apparatus, a reception apparatus, a programming unit in communication with the reception apparatus during a programming mode of operation, and a programming interface for passing signals between the programming unit and the reception apparatus during a programming mode of operation, wherein, during the programming mode of operation, at least a portion of the power-consuming electrical components of the reception apparatus are maintained in an off condition until at least one signal from the programming unit is received at the programming interface.
These and other objectives are achieved as is now described. When characterized broadly as a method, the present invention is directed to a method for communicating coded messages in a wellbore between a transmission node and a reception node, through a fluid column extending therebetween. The method is comprised of a plurality of method steps. A transmission apparatus is provided at the transmission node, which is in communication with the fluid column, for altering pressure of the fluid column to generate a coded message which is composed of either xe2x80x9cpositivexe2x80x9d or xe2x80x9cnegativexe2x80x9d rapid changes in pressure amplitude. A reception apparatus is also provided, but is disposed at the reception node. The reception apparatus includes: (1) a rigid structural component with an exterior surface which is in contact with the fluid column and an interior surface which is not in contact with the fluid column, and (2) a sensor assembly which detects changes in elastic deformation of the rigid structural component, which is also maintained out of contact with the fluid column. The transmission apparatus is utilized to alter pressure of the fluid column in a predetermined pattern to generate at least one coded message. The reception apparatus is utilized to detect the coded message in the fluid column through changes in the elastic deformation of the rigid structural component. In one embodiment, the sensor assembly includes a fluid body in communication with the interior surface of the rigid structural component, but which is not in communication with the fluid column. The fluid body is responsive to changes in the elastic deformation of the rigid structural component. Also, preferably, a pressure sensor is provided for directly sensing pressure changes in the fluid body to detect elastic deformation of the rigid structural component. In the alternative embodiment, a strain gage bridge may be utilized to detect elastic deformation of the rigid structural component. In the described embodiments of the present invention, the rigid structural component comprises a mandrel member which at least partially defines the central bore to the wellbore tubular member. The mandrel member is a substantially imperforate component which contains very few, if any, potential fluid leak paths, thus allowing the present invention to be utilized in wellbore completions which are intended for extremely long service lives.
In the present invention, the reception apparatus includes a processor which is programmed to identify particular electrical signal patterns developed by the reception apparatus in response to changes in the elastic deformation of the rigid structural component. The processor will perform particular predefined processor tasks in response to receipt of a coded message which it recognizes. For example, the processor may be programmed to provide an activation signal to at least one electrically-actuable wellbore tool. The actuation signal may be utilized to switch the electrically-actuable wellbore tool between selected operating modes.
In the preferred embodiment of the present invention, an electromagnetic programming interface is provided which is in electrical communication with the processor. The processor is programmed to provide a particular output in response to the receipt of particular electrical signals from the reception apparatus through an electromagnetic signal received by the electromagnetic program interface. This allows the processor to be programmed without having any direct electrical connection, thus eliminating a potential leak path.
In the preferred embodiment of the present invention, which is described, herein, said sensor assembly generates electrical signals corresponding to elastic deformation of the rigid structural component. The reception apparatus further includes signal processing for identifying and isolating rates of change in elastic deformation of the rigid structural component above and below predetermined rate thresholds. During the step of utilizing the reception apparatus to detect coded messages, the reception apparatus detects coded messages in the fluid column through rates of change in elastic deformation of the rigid structural component.
In the preferred embodiment of the present invention, the coded messages may be impressed upon the fluid column which serves as the transmission path through utilization of either a conventional triplex (or other) drilling rig pump or a pressure pulse generator apparatus especially adapted to develop rapid pressure changes without substantially changing the absolute volume of the fluid column.
The present invention may be utilized to perform completion operations in a wellbore. A single transmission apparatus is provided at the wellhead for generating coded signals which are transmitted to a plurality of reception apparatuses which are disposed at selected locations within a string of tubular members. A plurality of wellbore tools are provided in the string in selective communication with the plurality of reception apparatuses. The wellbore tools may include (a) electrically-actuable wellbore packers; (b) electrically-actuable perforating guns; (c) electrically-actuable vales; and (d) electrically-actuable liner hangers. The transmission apparatus may be utilized to generate particular coded messages to selectively actuate the plurality of wellbore tools in a predetermined manner to complete the wellbore. Typically, liner hangers may be utilized to hang casing off cemented casing segments. Cementing operations should follow to cement all portions of the casing. Next, perforating operations should be conducted to perforate selected portions of the cased wellbore. Then, one or more packers should be set to isolate particular regions between a production tubing string and the cased wellbore. Finally, valves should be opened to allow the selective flow of wellbore fluids into the cased wellbore for production upward through the production tubing string.
Additional objectives, features and advantages will be apparent in the written description which follows.